In recent years, the organic light emitting diode (OLED) has become a very popular new flat panel display product at home and abroad, because the OLED display has the characteristics of self-luminous, wide viewing angle, short reaction time, high luminous efficiency, wide color gamut, low working voltage, thin panel, capable of fabricating large size and flexible panel as well as simple fabrication process etc., moreover, it also has the potential of low cost.
In large size display applications e.g. OLED, since there is certain resistance in the backplane power line, and the drive currents of all pixels are provided by the power line voltage Vdd on the power line, the supply voltage of the area in the backplane that is close to the power supply location of the power line voltage Vdd is higher than the supply voltage of the area that is relatively far from the power supply location, such a phenomenon is called resistance drop (IR Drop). Since the power line voltage Vdd is associated with the current, the resistance drop will result in current difference in different areas, thereby generating the Mura phenomenon in display. The Mura phenomenon is well known in the art, it actually refers to human eye perceived difference in current and luminance of e.g. an OLED display. For example, as for an active matrix organic light emitting diode (AMOLED) device separately driven by the power line voltage Vdd of each row with a compensating circuit, FIG. 1 schematically shows the arrangement of lateral resistance distribution, longitudinal resistance distribution and light emitting diodes in pixels of the prior art. As shown in FIG. 1, the load RVdd in a line where the power line voltage Vdd locates e.g. comprises four loads, which are collectively referred to as the lateral resistance distribution, the loads each are represented by RVdd1, RVdd2, RVdd3, RVdd4 respectively.
The second line shows four light emitting diodes D1, D2, D3, D4. The arrangement in the third line is same as that in the first line, which is not shown. The four loads RVdd1, RVdd2, RVdd3, RVdd4 are all supplied with power by the power line voltage Vdd of the power line. In a particular case, the light emitting diodes D2, D3 do not need to emit light, the light emitting diodes D1, D4 emit light. Since each of the four loads RVdd1, RVdd2, RVdd3, RVdd4 generates a certain voltage drop, the distances of the light emitting diodes D1, D4 relative to the power line voltage Vdd are different, thus the voltages and currents provided to the light emitting diodes D1, D4 have been different, thereby even in the event that the light emitting diodes D1, D4 emit the same color, the light emitting diodes D1, D4 are different in luminance, i.e., the grey level is different, thereby the Mura phenomenon is generated. FIG. 2 schematically shows Mura generated by the pixels of the prior art according to FIG. 1 in the case of emitting light. Specifically, as shown in FIG. 2, there is no dark areas in the upper and lower two rows, i.e., the nth row and the n+2th row, the pixels in the two rows are in full bright, the areas 1 in the nth row and the n+2th row are both in full bright. The area 2 in the n+1th row is close to the power line voltage Vdd (IC binding area), the area 3 in the n+1th row is a dark area, there is no longitudinal resistance distribution, i.e., the light emitting diodes D2, D3 do not need to emit light, the light emitting diodes D1, D4 emit light, the longitudinal resistance distribution exists. Due to the presence of the four loads RVdd1, RVdd2, RVdd3, RVdd4, the luminance becomes dark gradually from the area 2 that is close to the power line voltage Vdd to the area 4 at a location relatively far from the power line voltage Vdd, i.e., the area 4 is darker then the area 2. The effect perceived by the human eyes is that the area 2 is much brighter than the area 1, the area 4 is a little brighter than the area 1, the area 3 is a dark area.
Therefore, it is urgently required in the prior art to improve the Mura phenomenon caused by resistance drop and the resulting crosstalk in image display.